1. Field of the Invention
The subject invention is directed to heater control structure for an ice protection system, and more particularly, to the architecture for a multi-zoned, multi-segmented heater control system for use in conjunction with an aircraft ice protection system.
2. Description of Related Art
Since the early days of powered aviation, aircraft have been troubled by the accumulation of ice on critical component surfaces such as wings and struts, under certain flight conditions. Unchecked, accumulations of ice can eventually so laden an aircraft with additional weight and so alter the aerofoil configuration of the wings as to precipitate an unacceptable flying condition. There are three generally accepted approaches that have developed to combat the accumulation of ice on component surfaces of an aircraft under flying conditions. These approaches include thermal de-icing, chemical de-icing and mechanical de-icing.
In the case of thermal de-icing, leading edges (i.e., the edges of an aircraft component on which ice accretes and are impinged upon by the air flowing over the aircraft and having a point at which this airflow stagnates) are heated to loosen adhesive forces between accumulating ice and the component surface. Once loosened, the ice is blown from the component surface by the airstream passing over the aircraft.
In one thermal de-icing approach, heaters are placed in the leading edge zone of the component, either by inclusion in a rubber boot applied over the leading edge of a wing or by incorporation into the skin structure of the component, such as on the leading edge of an engine nacelle. These heaters are typically powered by electrical energy derived from a generating source driven by one or more of the aircraft engines or an auxiliary power unit. The electrical energy is intermittently or continuously supplied to provide heat sufficient to prevent the formation of ice or to loosen accumulating ice.
Heaters used for ice protection on critical component surfaces, such as the leading edge surface of an engine nacelle are often comprised of an array of heater elements divided into multiple zones and segments. In prior art systems, groups of heaters within a particular zone or segment are independently controlled and/or scheduled. For example, in an array of fifteen heaters, there may be five independently controlled and scheduled groups of heaters. This type of distributed architecture is relatively complex in that it requires separate circuitry to drive each group of heaters. This results in an undesirably large and heavy hardware package in an environment where minimizing size and weight is preferable. Furthermore, because each group of heaters in the array is independently driven, the failure of a controller or scheduler in any one group will render that group inoperable. In other words, prior art distributed heater control systems do not have redundant control and/or scheduling capabilities.
It would be beneficial therefore to provide heater control architecture for a multi-zoned, multi-segmented ice protection system that has reduced complexity, size and weight relative to prior art heater control architecture, and provides redundant heater control and scheduling capability.